The present invention relates to single-cylinder, truck-mounted brake rigging and, particularly, to such a rigging arrangement in which force-transmitting members pass through openings in the truck bolster to apply braking force to conventional, truss-type brake beams located on opposite sides of the bolster.
A brake rigging of the aforementioned-type is shown in U.S. Pat. No. 4,613,016 and comprises, in addition to the brake beams, a force-transfer lever that is pivotally-connected to each brake beam at its midpoint, with the corresponding lever arms of these force-transfer levers being connected to the force-transmitting members. One force-transmitting member comprises a slack adjuster device, such as that disclosed in copending U.S. application Ser. No. 714,596. The other force-transmitting member includes a brake cylinder device, the body of which is mounted on one brake beam between the beam tension and compression members adjacent the strut bar, and a connecting rod between the transfer lever arm of the other brake beam and the cylinder body. The brake cylinder piston push rod is connected to the transfer lever arm of the one brake beam. Because of space limitations dictated by the cylinder location between the beam tension and compression members, the size of the brake cylinder is such that force amplification is required to obtain the desired brake forces. In addition, the size of the bolster openings is restrictive with respect to the force-transmitting members passing through these openings. This is especially true when a slack adjuster device is employed as the one force-transmitting member, due to the relatively large diameter of slack adjusters. Accordingly, the arcuate swing of the transfer levers, as they rotate from brake-release to brake-application positions through the range of new to condemned conditions of brake shoe/wheel wear, and the consequent bailing action of the slack adjuster, makes this restriction of the bolster opening especially critical. This is even more significant due to the fact that over-travel of the brake cylinder piston beyond a nominal piston stroke must be provided in accordance with A.A.R. requirements, in order to take up slack due to brake shoe/wheel wear, in the event of slack adjuster failure. This over-travel of the effective piston stroke increases the arcuate swing of the transfer levers and, accordingly, further increases the bailing action of the force-transmitting members. Moreover, the arcuate swing of the respective transfer levers differs as brake shoe/wheel wear progresses, since only the transfer lever associated with the non-cylinder brake beam is affected by the slack adjuster action, while the arcuate swing of the other transfer lever remains the same throughout the brake shoe/wheel wear range. Thus, not only does the degree of bailing action of the force-transmitting members change, but the force-transmitting members tend to assume a cocked disposition with respect to the opening through the bolster, as the angularity of the one transfer lever changes relative to the other. Due to this cocked disposition and lateral swing, particularly when the force-transmitting member is the slack adjuster, clearance with the bolster opening is made even more critical.